Orthogonal frequency division multiplexing (OFDM) is a particular form of frequency division multiplexing that distributes data over a number of carriers that have a very precise spacing in the frequency domain. The precise spacing and partially overlapping spectra of the carriers provides several benefits such as high spectral efficiency, resiliency to radio frequency interference and lower multi-path distortion. Due to its beneficial properties and superior performance in multi-path fading wireless channels, OFDM has been identified as a useful technique in the area of high data-rate wireless communication, for example wireless metropolitan area networks (MAN). Wireless MAN are networks to be implemented over an air interface for fixed, portable, and mobile broadband access systems.
In another type of frequency division multiplexing, rather than using closely spaced frequencies of OFDM, the spectra of adjacent channels are more or less distinct, and bandpass filtering is typically employed to separate channels. This will be referred to as “conventional frequency division multiplexing”.
Orthogonal frequency division multiplexing is beneficial in that multiple input multiple output (MIMO) and collaborative MIMO transmission schemes are easily implemented thereon. Furthermore, the use of orthogonal frequency division multiplexing allows for flexible and efficient pilot designs. Also, problems related to noise enhancement can be avoided during signal processing at the receiver.
The use of conventional frequency division multiplexing has a lower Peak to Average Power Ratio (PAPR). A disadvantage is that it causes noise enhancement.